Atoms, Molecules and Ions Dalton`s Atomic Theory (1808)
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Slide 1 ___________________________________ ___________________________________ ___________________________________ ___________________________________ Atoms, Molecules and Ions ___________________________________ Chapter 2 Section 2.1 – 2.6 for Test II ___________________________________ ___________________________________ Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Slide 2 Dalton’s Atomic Theory (1808) ___________________________________ 1. Elements are composed of extremely small particles called atoms. 2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements. Slide 3 ___________________________________ ___________________________________ ___________________________________ 3. Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction. ___________________________________ 4. A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction. ___________________________________ ___________________________________ 2 ___________________________________ Dalton’s Atomic Theory ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Law of Multiple Proportions 3 Slide ___________________________________ 4 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 16 X + 8Y 8 X2Y ___________________________________ Law of Conservation of Mass 4 Slide 5 ___________________________________ Cathode Ray Tube ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ J.J. Thomson, measured mass/charge of e(1906 Nobel Prize in Physics) Slide ___________________________________ 5 ___________________________________ Cathode Ray Tube 6 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 6 Slide ___________________________________ Millikan’s Experiment 7 ___________________________________ Measured mass of e- ___________________________________ (1923 Nobel Prize in Physics) ___________________________________ ___________________________________ ___________________________________ e- charge = -1.60 x 10-19 C ___________________________________ Thomson’s charge/mass of e- = -1.76 x 108 C/g e- mass = 9.10 x 10-28 g Slide 8 7 ___________________________________ Types of Radioactivity ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ (uranium compound) 8 Slide ___________________________________ Thomson’s Model 9 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 9 Slide 10 ___________________________________ Rutherford’s Experiment ___________________________________ (1908 Nobel Prize in Chemistry) ___________________________________ ___________________________________ ___________________________________ particle velocity ~ 1.4 x 107 m/s (~5% speed of light) 1. atoms positive charge is concentrated in the nucleus 2. proton (p) has opposite (+) charge of electron (-) 3. mass of p is 1840 x mass of e- (1.67 x 10-24 g) 10 Slide Rutherford’s Model of the Atom 11 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ atomic radius ~ 100 pm = 1 x 10-10 m ___________________________________ nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m ___________________________________ “If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.” 11 Slide 12 ___________________________________ ___________________________________ Chadwick’s Experiment (1932) (1935 Noble Prize in Physics) ___________________________________ ___________________________________ H atoms - 1 p; He atoms - 2 p mass He/mass H should = 2 ___________________________________ measured mass He/mass H = 4 + 9Be 1n ___________________________________ ___________________________________ + 12C + energy ___________________________________ neutron (n) is neutral (charge = 0) n mass ~ p mass = 1.67 x 10-24 g 12 Slide ___________________________________ 13 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ mass p ≈ mass n ≈ 1840 x mass e- ___________________________________ 13 Slide 14 Atomic number, Mass number and Isotopes ___________________________________ ___________________________________ Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons ___________________________________ = atomic number (Z) + number of neutrons Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei Mass Number 1 1H 235 92 Slide 15 ___________________________________ A ZX Atomic Number 2 1H U ___________________________________ Element Symbol ___________________________________ (D) 238 92 3 1H (T) U ___________________________________ 14 ___________________________________ The Isotopes of Hydrogen ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 15 Slide ___________________________________ 16 How many protons, neutrons, and electrons are 14 in 6 C ? ___________________________________ ___________________________________ 6 protons, 8 (14 – 6) neutrons, 6 electrons ___________________________________ ___________________________________ How many protons, neutrons, and electrons are 11 in 6 C ? 6 protons, 5 (11 – 6) neutrons, 6 electrons ___________________________________ ___________________________________ 16 Slide ___________________________________ The Modern Periodic Table 17 Noble Gas Period Halogen Group Alkali Metal Alkali Earth Metal ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 17 Slide 18 A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical forces ___________________________________ ___________________________________ ___________________________________ H2 H2O NH3 CH4 ___________________________________ A diatomic molecule contains only two atoms ___________________________________ H2, N2, O2, Br2, HCl, CO ___________________________________ diatomic elements A polyatomic molecule contains more than two atoms O3, H2O, NH3, CH4 18 ___________________________________ Slide 19 ___________________________________ An ion is an atom, or group of atoms, that has a net positive or negative charge. cation – ion with a positive charge If a neutral atom loses one or more electrons it becomes a cation. ___________________________________ ___________________________________ ___________________________________ Na 11 protons 11 electrons Na+ 11 protons 10 electrons anion – ion with a negative charge If a neutral atom gains one or more electrons it becomes an anion. Cl 17 protons 17 electrons Cl– ___________________________________ ___________________________________ ___________________________________ 17 protons 18 electrons 19 Slide ___________________________________ 20 ___________________________________ A monatomic ion contains only one atom Na+, Cl-, Ca2+, O2-, Al3+, N3- ___________________________________ ___________________________________ ___________________________________ A polyatomic ion contains more than one atom OH-, CN-, NH4+, NO3- ___________________________________ ___________________________________ 20 Slide 21 ___________________________________ Common Ions Shown on the Periodic Table ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 21 Slide ___________________________________ 22 How many protons and electrons are in 27 3+ 13 Al ___________________________________ ? ___________________________________ 13 protons, 10 (13 – 3) electrons ___________________________________ ___________________________________ How many protons and electrons are in 78 234 Se ? ___________________________________ 34 protons, 36 (34 + 2) electrons ___________________________________ 22 Slide 23 ___________________________________ Formulas and Models ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 23 Slide 24 ___________________________________ A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance ___________________________________ ___________________________________ An empirical formula shows the simplest whole-number ratio of the atoms in a substance ___________________________________ molecular empirical H2O H2O C6H12O6 CH2O ___________________________________ O3 O ___________________________________ N2H4 NH2 ___________________________________ 24 Slide 25 ___________________________________ Ionic compounds consist of a combination of cations and an anions ___________________________________ • The formula is usually the same as the empirical formula ___________________________________ • The sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero ___________________________________ The ionic compound NaCl ___________________________________ ___________________________________ ___________________________________ 25 Slide ___________________________________ 26 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ The most reactive metals (green) and the most reactive nonmetals (blue) combine to form ionic compounds. ___________________________________ 26 Slide 27 ___________________________________ Formula of Ionic Compounds ___________________________________ 2 x +3 = +6 3 x -2 = -6 Al2O3 Al3+ 1 x +2 = +2 Ca2+ ___________________________________ O2- ___________________________________ 2 x -1 = -2 CaBr2 ___________________________________ Br- ___________________________________ 1 x +2 = +2 Na+ 1 x -2 = -2 Na2CO3 ___________________________________ CO3227 Slide 28 ___________________________________ CH-2 HW ___________________________________ Questions and Problems Pages 55 - 56 ___________________________________ ___________________________________ 2.8, 2.12, 2.12, 2.14, 2.16, 2.22, 2.24. ___________________________________ ___________________________________ ___________________________________ 28
